Came across this about a week ago. Atlantic Fleet, its available on steam. I bought it for £3.95 in the sale, its now back up to £6.99. Its the best £3.95 I have spent in a long time.

Its a turn based strategy game around the Battle of the Atlantic in WW2. You can play either side, in single scenarios or a full dynamic campaign. You earn 'Renown Points' by sinking ships. You then spend those point to build up your fleet. Ship/Classes come into play at the historical time. So you cant have Bismarck until August 1940, and if you loose it, tough, you cant get it back.

The gameplay is slightly simplistic, but that's no bad thing in this case. Anyway, I am having a blast. Thought it was worth mentioning.